This invention relates to a variable displacement pump system with an override destroking system.
In conventional axial piston pumps, destroking is achieved by connecting the swashplate or stroke control pistons to sump or drain. With such a destroking system, the time required to fully destroke the pump may be longer than desired. Another axial piston variable displacement pump has a pressure-responsive stroke control device which is exposed to charge fluid pressure for control and which may be exposed to system pressure for override destroking. However, in this system, the override pressure has to work in opposition to the control pressure, resulting in a somewhat inefficient destroking function. One solution to this problem is described in copending U.S. patent application, Ser. No. 576,686, wherein pump workport pressure is used for stroke control and for override destroking. It would be desirable to enhance such a system by providing means for assuring that a vehicle driven by such a system can be positively stopped when the control valve is in neutral. It would further be desirable to add acceleration control capabilities to such a system.